GB1108499A - Cooling system for nuclear reactors - Google Patents

Abstract

1,108,499. Reactors. EUROPEAN ATOM ENERGY COMMUNITY (EURATOM). 13 Dec., 1965 [14 Dec., 1964], No. 52862/65. Heading G6C. A nuclear reactor has one or more heat pipes as a means for extracting the heat of reaction. A heat pipe is a heat transfer device comprising a container, condensable vapour, and capillary means disposed within the container for the transport of the condensed vapour from a cooler region of the container to a hotter region. The vapour is driven from the hotter region to the cooler region by the difference in vapour pressure. The temperature drop along the heat pipe is powers of ten lower than in the case of conventional heat transports and a nearly uniform temperature distribution is therefore established along the entire pipe surface. In a specific example, portions of heat pipes are disposed in, and thermally coupled to, passageways in the fuel elements, moderator and reflector of a reactor core to form evaporator regions, the non-coupled portions extending outwardly from the reactor core to form condenser regions. The inner walls of the heat pipes are covered with wicks, e.g. of niobium, of suitable capillary structure, the pores sizes of the wicks being sufficiently small to produce capillary action. Tubular fuel elements may be separately mounted on the heat pipes or the fuel may be coated directly on the outer surfaces of the heat pipes. A suitable fuel is a Mo-UO 2 , cermet. The fuel heat pipes are preferably of Ta and contain Ag as the heat carrier fluid, operating at a temperature of about 1800‹ C., while the moderator and reflector heat pipes are preferably of Nb and contain Cs as the heat carrier fluid. The moderator is ZrH 2 and is separated from the fuel elements by electrical insulation and thermal shields. The condenser regions of the fuel heat pipes each terminate in an emitter electrode of a thermionic converter. The front faces of the heat pipes can each directly constitute an emitter electrode or be vapour-plated with an electron emissive layer. The collector electrodes of the thermionic converter are each coupled to a heat pipe for the removal of heat generated. The collector heat pipes are preferably formed of Nb- Zr alloy and contain Li as the heat carrier fluid.